<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <script src="./vue.js"></script>

</head>
<body>
  <div id="box">
    <button @click.once="change">显示</button>
  </div>

  <script>


    let vm = new Vue({
      el:"#box",
      data:{  
        msg:"msg",
        show:false
      },
      methods:{
        change(){
         alert(1)
        }
      }
    });

  
    console.log(vm);
  </script>
</body>
</html>